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Sep 22, 2013
09/13

by
Peter G. Casazza; Gitta Kutyniok; Darrin Speegle; Janet C. Tremain

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In this paper we study the Feichtinger Conjecture in frame theory, which was recently shown to be equivalent to the 1959 Kadison-Singer Problem in $C^{*}$-Algebras. We will show that every bounded Bessel sequence can be decomposed into two subsets each of which is an arbitrarily small perturbation of a sequence with a finite orthogonal decomposition. This construction is then used to answer two open problems concerning the Feichtinger Conjecture: 1. The Feichtinger Conjecture is equivalent to...

Source: http://arxiv.org/abs/math/0702216v1

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Sep 22, 2013
09/13

by
E. Prodan; R. Car

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Inspired by the work of Kamenev and Kohn, we present a general discussion of the two-terminal dc conductance of molecular devices within the framework of Time Dependent Current-Density Functional Theory. We derive a formally exact expression for the adiabatic conductance and we discuss the dynamical corrections. For junctions made of long molecular chains that can be either metallic or insulating, we derive the exact asymptotic behavior of the adiabatic conductance as a function of the chain's...

Source: http://arxiv.org/abs/cond-mat/0702192v1

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Sep 22, 2013
09/13

by
R. Sharma; S. D. Maharaj

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By assuming a particular mass function we find new exact solutions to the Einstein field equations with an anisotropic matter distribution. The solutions are shown to be relevant for the description of compact stars. A distinguishing feature of this class of solutions is that they admit a linear equation of state which can be applied to strange stars with quark matter.

Source: http://arxiv.org/abs/gr-qc/0702046v1

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Sep 18, 2013
09/13

by
Ralf Schiffler

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We consider the Ptolemy cluster algebras, which are cluster algebras of finite type $A$ (with non-trivial coefficients) that have been described by Fomin and Zelevinsky using triangulations of a regular polygon. Given any seed $\zS$ in a Ptolemy cluster algebra, we present a formula for the expansion of an arbitrary cluster variable in terms of the cluster variables of the seed $\zS$. Our formula is given in a combinatorial way, using paths on a triangulation of the polygon that corresponds to...

Source: http://arxiv.org/abs/math/0611956v2

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Sep 22, 2013
09/13

by
Fabio Lepreti; Vincenzo Carbone; Pierluigi Veltri

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Modeling the intermittent behavior of turbulent energy dissipation processes both in space and time is often a relevant problem when dealing with phenomena occurring in high Reynolds number flows, especially in astrophysical and space fluids. In this paper, a dynamical model is proposed to describe the spatio-temporal intermittency of energy dissipation rate in a turbulent system. This is done by using a shell model to simulate the turbulent cascade and introducing some heuristic rules, partly...

Source: http://arxiv.org/abs/nlin/0702015v1

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Sep 22, 2013
09/13

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Sibasish Laha; Taparati Gangopadhyay; Manjari Bagchi; Mira Dey; Jishnu Dey; Monika Sinha; Subharthi Ray

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At finite temperature (T) there is a link with general relativity and hydrodynamics that leads to a lower bound for the ratio of shear viscosity and entropy density (\eta/s). We find that the bound is saturated in the simple model for quark matter that we use for strange stars at T = 80 MeV, at the surface of a strange star. At this T we have the possibility of cosmic separation of phases. We find that, although strongly correlated, the quark matter at the surface of strange stars constitute...

Source: http://arxiv.org/abs/hep-ph/0702086v1

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Sep 22, 2013
09/13

by
Stephon Alexander; Deepak Vaid

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In a recent paper we discovered that a fermionic condensate is formed from gravitational interactions due to the covariant coupling of fermions in the presence of a torsion-fermion contact interaction. The condensate gap gives a negative contribution to the bare cosmological constant. In this letter, we show that the cosmological constant problem can be solved without fine tuning of the bare cosmological constant. We demonstrate how a universe with a large initial cosmological constant...

Source: http://arxiv.org/abs/hep-th/0702064v2

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Sep 20, 2013
09/13

by
Dmitry V. Yakubovich

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A functional model for nondissipative unbounded perturbations of an unbounded self-adjoint operator on a Hilbert space X is constructed. This model is analogous to the Nagy--Foias model of dissipative operators, but it is linearly similar and not unitarily equivalent to the operator. It is attached to a domain of parabolic type, instead of a half-plane. The transformation map from X to the model space and the analogue of the characteristic function are given explicitly. All usual consequences...

Source: http://arxiv.org/abs/math/0607062v2

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Sep 22, 2013
09/13

by
Lyonell Boulton; Peter Lancaster

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The theme of this paper was motivated by the question: How effective are path-following procedures for tracing the pseudospectral boundary? The present study of the mathematical properties of the boundary of the pseudospectrum is the result. This boundary is generally made up piecewise smooth curves. We shown how the Schur triangular form of the matrix can be used to analyse dynamical properties of the singular points on these curves.

Source: http://arxiv.org/abs/math/0702218v1

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Sep 22, 2013
09/13

by
Joachim Ankerhold; Eli Pollak

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Usually one finds that dissipation tends to make a quantum system more classical in nature. In this paper we study the effect of momentum dissipation on a quantum system. The momentum of the particle is coupled bilinearly to the momenta of a harmonic oscillator heat bath. For a harmonic oscillator system we find that the position and momentum variances for momentum coupling are respectively identical to momentum and position variances for spatial friction. This implies that momentum coupling...

Source: http://arxiv.org/abs/cond-mat/0702205v1

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Sep 18, 2013
09/13

by
Daw-Wei Wang

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We investigate the quantum phase transitions of bosonic polar molecules in a two-dimensional double layer system. We show that an interlayer bound state of dipoles (dimers) can be formed when the dipole strength is above a critical value, leading to a zero-energy resonance in the interlayer s-wave scattering channel. In the positive detuning side of the resonance, the strong repulsive interlayer pseudopotential can drive the system into a maximally entangled state, where the wave function is a...

Source: http://arxiv.org/abs/cond-mat/0611394v3

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Sep 22, 2013
09/13

by
Gopal Dixit; B. K. Sahoo; P. C. Deshmukh; R. K. Chaudhuri; Sonjoy Majumder

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Accurate {\it ab initio} calculations have been carried out to study the valence electron removal energies and oscillator strengths of astrophysically important electromagnetic transitions of quadruply ionized vanadium, $V^{4+}$. Many important electron correlations are considered to all-orders using the relativistic coupled-cluster theory. Calculated ionization potentials and fine structure splittings are compared with the experimental values, wherever available. To our knowledge, oscillator...

Source: http://arxiv.org/abs/physics/0702066v1

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Sep 22, 2013
09/13

by
Jennifer Kreft; Yeng-Long Chen

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The Ludwig-Soret effect, the migration of a species due to a temperature gradient, has been extensively studied without a complete picture of its cause emerging. Here we investigate the dynamics of DNA and spherical particles sub jected to a thermal gradient using a combination of Brownian dynamics and the lattice Boltzmann method. We observe that the DNA molecules will migrate to colder regions of the channel, an observation also made in the experiments of Duhr, et al[1]. In fact, the thermal...

Source: http://arxiv.org/abs/cond-mat/0702194v1

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Sep 20, 2013
09/13

by
Maria J. Cruz; Matt J. Jarvis; Steve Rawlings; Katherine M. Blundell

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We use the 6C** sample to investigate the co-moving space density of powerful, steep-spectrum radio sources. This sample, consisting of 68 objects, has virtually complete K-band photometry and spectroscopic redshifts for 32 per cent of the sources. In order to find its complete redshift distribution, we develop a method of redshift estimation based on the K-z diagram of the 3CRR, 6CE, 6C* and 7CRS radio galaxies. Based on this method, we derive redshift probability density functions for all the...

Source: http://arxiv.org/abs/astro-ph/0612268v2

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Sep 22, 2013
09/13

by
Samuel Alexandre Vidal

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In this article we give a classification of the sub-groups in PSL(2,Z) and of the conjugacy classes of these sub-groups by the mean of an combinatorial invariant: some trivalent diagrams (dotted or not). We give explicit formulae enabling to count the number of isomorphism classes of these structures and of some of their variations, as function of the number of their arcs. Until now, the counting of non-dotted diagrams was an open problem, for it gives also the number of unrooted combinatorial...

Source: http://arxiv.org/abs/math/0702223v1

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Sep 20, 2013
09/13

by
Gor Sarkissian

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We study Cardy states in the (2,2,2,2) Gepner model from the algebraic and geometric sides. We present the full list of primaries of this model together with their characters. The effects of fixed point resolution are analyzed. Annulus partition function between various Cardy states are calculated. Using the equivalent description in terms of $T^4/Z_4$ the corresponding geometrical realization is partially found.

Source: http://arxiv.org/abs/hep-th/0612058v4

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Sep 19, 2013
09/13

by
Takayuki Matsuki; Toshiyuki Morii; Kazutaka Sudoh

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Recent discovery of D_s states suggests existence of radial excitations. Our semirelativistic quark potential model succeeds in reproducing these staes within one to two percent of accuracy compared with the experiments, D_s0(2860) and D_s^*(2715), which are identified as 0^+ and 1^- radial excitations (n=2). We also present calculations of radial excitations for B/B_s heavy mesons. Relation between our formulation and the modified Goldberger-Treiman relation is also described.

Source: http://arxiv.org/abs/hep-ph/0610186v3

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Sep 22, 2013
09/13

by
Robert K. Hladky; Scott D. Pauls

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We derive a formula for the first variation of horizontal perimeter measure for $C^2$ hypersurfaces of completely general sub-Riemannian manifolds, allowing for the existence of characteristic points. For $C^2$ hypersurfaces in vertically rigid sub-Riemannian manifolds we also produce a second variation formula for variations supported away from the characteristic locus. This variation formula is used to show the bubble sets in \hn{2} are stable under volume preserving variations.

Source: http://arxiv.org/abs/math/0702237v1

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Sep 22, 2013
09/13

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S. Wycech; F. J. Hartmann; J. Jastrzebski; B. Klos; A. Trzcinska; T. von Egidy

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The recent and older level shifts and widths in pbar atoms are analyzed. The results are fitted by an antiproton-nucleus optical potential with two basic complex strength parameters. These parameters are related to average S and P wave scattering parameters in the subthreshold energy region. A fair consistency of the X-ray data for all Z values, stopping pbar data and the Nbar-N scattering data has been achieved. The determination of neutron density profiles at the nuclear surface is...

Source: http://arxiv.org/abs/nucl-th/0702029v1

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Sep 22, 2013
09/13

by
S. W. Hong; C. H. Hyun; C. Y. Ryu

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We use the modified quark-meson coupling and the quantum hadrodynamics models to study the properties of neutron star. Coupling constants of both models are adjusted to reproduce the same saturation properties. The onset of kaon condensation in neutron star matter is studied in detail over a wide range of kaon optical potential values. Once the kaon condensation takes place, the population of kaons increases very rapidly, and kaons become the dominant component, possibly making the neutron star...

Source: http://arxiv.org/abs/nucl-th/0702028v1

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Sep 22, 2013
09/13

by
D. De Silva; O. Savin

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We prove that entire bounded monotone solutions to a certain class of fully nonlinear equations in 2D are one-dimensional. Our result also gives a new (non-variational) proof of the well known De Giorgi's conjecture.

Source: http://arxiv.org/abs/math/0702231v1

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Sep 22, 2013
09/13

by
Yuriy V. Pershin

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A pulsed technique for electrons in 2D systems, in some ways analogous to spin echo in nuclear magnetic resonance, is discussed. We show that a sequence of optical below-band gap pulses can be used to suppress the electron spin relaxation due to the D'yakonov-Perel' spin relaxation mechanism. The spin relaxation time is calculated for several pulse sequences within a Monte Carlo simulation scheme. The maximum of spin relaxation time as a function of magnitude/width of the pulses corresponds to...

Source: http://arxiv.org/abs/cond-mat/0310225v2

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Sep 22, 2013
09/13

by
D. S. O'Brien; N. H. Buttimore

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The PAX project at GSI Darmstadt plans to polarize an antiproton beam by repeated interaction with a hydrogen target in a storage ring. Many of the beam particles are required to remain within the ring after interaction with the target, so small scattering angles are important. Hence we concentrate on low momentum transfer (small t), a region where electromagnetic effects dominate the hadronic effects. A colliding beam of polarized electrons with energy sufficient to provide scattering of...

Source: http://arxiv.org/abs/hep-ph/0702088v1

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Sep 20, 2013
09/13

by
L. Giusti; P. Hernandez; M. Laine; C. Pena; J. Wennekers; H. Wittig

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We compute the leading-order low-energy constants of the DeltaS=1 effective weak Hamiltonian in the quenched approximation of QCD with up, down, strange, and charm quarks degenerate and light. They are extracted by comparing the predictions of finite volume chiral perturbation theory with lattice QCD computations of suitable correlation functions carried out with quark masses ranging from a few MeV up to half of the physical strange mass. We observe a large DeltaI=1/2 enhancement in this corner...

Source: http://arxiv.org/abs/hep-ph/0607220v2

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Sep 18, 2013
09/13

by
Han-Ying Guo; Bin Zhou; Yu Tian; Zhan Xu

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The conformal extensions of three kinds of special relativity with ISO(1,3)/SO(1,4)/SO(2,3) invariance on Mink/dS/AdS space, respectively, are realized on an SO(2,4)/Z_2 invariant projective null cone [N] as the (projective) boundary of the 5-d AdS-space. The relations among the conformal Mink/dS/AdS spaces, the motions of light signals and the conformal field theories on them can be given. Thus, there should be a triality for these conformal issues and the conjectured AdS/CFT correspondence.

Source: http://arxiv.org/abs/hep-th/0611047v2

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Sep 19, 2013
09/13

by
Deog Ki Hong; Mannque Rho; Ho-Ung Yee; Piljin Yi

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We study baryons in an AdS/CFT model of QCD by Sakai and Sugimoto, realized as small instantons with fundamental string hairs. We introduce an effective field theory of the baryons in the five-dimensional setting, and show that the instanton interpretation implies a particular magnetic coupling. Dimensional reduction to four dimensions reproduces the usual chiral effective action, and in particular we estimate the axial coupling $g_A$ between baryons and pions and the magnetic dipole moments,...

Source: http://arxiv.org/abs/hep-th/0701276v2

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Sep 20, 2013
09/13

by
Jiangyong Jia; Chun Zhang

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We find that a simple extension of the coalescence model is sufficient to incorporate the perfect quark number scaling behavior of the elliptic flow in transverse kinetic energy, recently discovered by the PHENIX Collaboration. The flavor dependence of the elliptic flow can be consistently described in the low and intermediate $p_T$ if the transverse kinetic energy is conserved in the $2\to1$ or $3\to1$ parton coalescence process at the hadronization. Thus suggesting the quark coalescence as a...

Source: http://arxiv.org/abs/hep-ph/0608187v2

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Sep 20, 2013
09/13

by
Pierre Ca Grange; Ernst Werner

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Quantum Field Theory with fields as Operator Valued Distributions with adequate test functions, -the basis of Epstein-Glaser approach known now as Causal Perturbation Theory-, is recalled. Its recent revival is due to new developments in understanding its renormalization structure, which was a major and somehow fatal disease to its widespread use in the seventies. In keeping with the usual way of definition of integrals of differential forms, fields are defined through integrals over the whole...

Source: http://arxiv.org/abs/math-ph/0612011v2

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Sep 22, 2013
09/13

by
M. Roellig; N. P. Abel; T. Bell; F. Bensch; J. Black; G. J. Ferland; B. Jonkheid; I. Kamp; M. J. Kaufman; J. Le Bourlot; F. Le Petit; R. Meijerink; O. Morata; V. Ossenkopf; E. Roueff; G. Shaw; M. Spaans; A. Sternberg; J. Stutzki; W. -F. Thi; E. F. van Dishoeck; P. A. M. van Hoof; S. Viti; M. G. Wolfire

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We present a comparison between independent computer codes, modeling the physics and chemistry of interstellar photon dominated regions (PDRs). Our goal was to understand the mutual differences in the PDR codes and their effects on the physical and chemical structure of the model clouds, and to converge the output of different codes to a common solution. A number of benchmark models have been created, covering low and high gas densities and far ultraviolet intensities. The benchmark models were...

Source: http://arxiv.org/abs/astro-ph/0702231v1

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Sep 19, 2013
09/13

by
A. Bassi

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We review the major achievements of the dynamical reduction program, showing why and how it provides a unified, consistent description of physical phenomena, from the microscopic quantum domain to the macroscopic classical one. We discuss the difficulties in generalizing the existing models in order to comprise also relativistic quantum field theories. We point out possible future lines of research, ranging from mathematical physics to phenomenology.

Source: http://arxiv.org/abs/quant-ph/0701014v2

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Sep 19, 2013
09/13

by
A. M. Moro; M. Rodriguez-Gallardo; R. Crespo; I. J. Thompson

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Benchmark calculations are performed aiming to test the use of two different pseudo-state bases on the the Multiple Scattering expansion of the total Transition amplitude (MST) scattering framework. Calculated differential cross sections for p-6He inelastic scattering at 717 MeV/u show a good agreement between the observables calculated in the two bases. This result gives extra confidence on the pseudo-state representation of continuum states to describe inelastic/breakup scattering.

Source: http://arxiv.org/abs/nucl-th/0610059v2

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Sep 18, 2013
09/13

by
V. V. Kiselev

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For evolution of flat universe, we classify late time and future attractors with scaling behavior of scalar field quintessence in the case of potential, which, at definite values of its parameters and initial data, corresponds to exact scaling in the presence of cosmological constant.

Source: http://arxiv.org/abs/gr-qc/0611064v3

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Jul 20, 2013
07/13

by
Takamasa Chiba; Tatsunori Imai; Hideki Asada

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None of N-body gravitating systems have been considered to emit periodic gravitational waves because of their chaotic orbits when N=3 (or more). We employ a figure-eight orbit as a specific model for a 3-body system in order to illustrate that some of triple stars are capable of generating periodic waves. This illustration would imply that a certain class of N-body gravitating systems may be relevant to the gravitational waves generation. We show also that the total angular momentum of this...

Source: http://arxiv.org/abs/astro-ph/0609773v4

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Sep 22, 2013
09/13

by
Ph. Boucaud; J. P. Leroy; A. Le Yaouanc; A. Y. Lokhov; J. Micheli; O. Pène; J. Rodríguez-Quintero; C. Roiesnel

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We exploit the Ward-Slavnov-Taylor identity relating the 3-gluons to the ghost-gluon vertices to conclude either that the ghost dressing function is finite and non vanishing at zero momentum while the gluon propagator diverges (although it may do so weakly enough not to be in contradiction with current lattice data) or that the 3-gluons vertex is non-regular when one momentum goes to zero. We stress that those results should be kept in mind when one studies the Infrared properties of the ghost...

Source: http://arxiv.org/abs/hep-ph/0702092v1

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Sep 22, 2013
09/13

by
Peter Steinberg

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The experimental and theoretical status of the ``near perfect fluid'' at RHIC is discussed. While the hydrodynamic paradigm for understanding collisions at RHIC is well-established, there remain many important open questions to address in order to understand its relevance and scope. It is also a crucial issue to understand how the early equilibration is achieved, requiring insight into the active degrees of freedom at early times.

Source: http://arxiv.org/abs/nucl-ex/0702020v1

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Sep 22, 2013
09/13

by
R. H. France III; E. L. Wilds; J. E. McDonald; M. Gai

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We measured the beta-delayed alpha-particle emission spectrum of 16N with a sensitivity for beta-decay branching ratios of the order of 10-10. The 16N nuclei were produced using the d(15N,16N)p reaction with 70 MeV 15N beams and a deuterium gas target 7.5 cm long at a pressure of 1250 torr. The 16N nuclei were collected (over 10 s) using a thin aluminum foil with an areal density of 180 mu g/cm2 tilted at 7 Deg with respect to the beam. The activity was transferred to the counting area by means...

Source: http://arxiv.org/abs/nucl-ex/0702018v1

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Sep 20, 2013
09/13

by
CDF Collaboration

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A search for a manifestly exotic S=-2 baryon state decaying to Xi- pi-, and its neutral partner decaying to Xi- pi+, has been performed using 220 pb^(-1) of pp= collisions at sqrt(s)=1.96 TeV collected by the Collider Detector at Fermilab. The Xi trajectories were measured in a silicon tracker before their decay, resulting in a sample with low background and excellent position resolution. No evidence was found for S=-2 pentaquark candidates in the invariant mass range of 1600--2100 MeV/c^2...

Source: http://arxiv.org/abs/hep-ex/0612066v3

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Sep 22, 2013
09/13

by
Hamadi Abidi; Taoufik Hmidi

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We prove the global well-posedness of the critical dissipative quasi-geostrophic equation for large initial data belonging to the critical Besov space $\dot B^0_{\infty,1}(\RR^2).$

Source: http://arxiv.org/abs/math/0702215v1

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Sep 22, 2013
09/13

by
Ken Wakita; Toshiyuki Tsurumi

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Community analysis algorithm proposed by Clauset, Newman, and Moore (CNM algorithm) finds community structure in social networks. Unfortunately, CNM algorithm does not scale well and its use is practically limited to networks whose sizes are up to 500,000 nodes. The paper identifies that this inefficiency is caused from merging communities in unbalanced manner. The paper introduces three kinds of metrics (consolidation ratio) to control the process of community analysis trying to balance the...

Source: http://arxiv.org/abs/cs/0702048v1

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Sep 22, 2013
09/13

by
M. Sharif

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Perfect-fluid, static, cylindrically symmetric solutions of Einstein's field equations are obtained for the equations of state $\rho+3p=0$ and $\rho=p$. In the former case, the density and the pressure turn out to be constant while in the later case, they depend on the radial parameter $r$. Evan's solution corresponding to the equation of state $\rho=p$ is included in the solutions discussed here.

Source: http://arxiv.org/abs/gr-qc/0702045v1

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Sep 22, 2013
09/13

by
S. R. Federman; M. Brown; S. Torok; S. Cheng; R. E. Irving; R. M. Schectman; L. J. Curtis

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We report lifetimes, branching fractions, and the resulting oscillator strengths for transitions within the P II multiplet (3s^23p^2 ^3P - 3s^23p4s ^3P^o) at 1154 A. These beam-foil measurements represent the most comprehensive and precise set currently available experimentally. Comparison with earlier experimental and theoretical results is very good. Since Morton's most recent compilation is based on the earlier body of results, phosphorus abundances for interstellar material in our Galaxy...

Source: http://arxiv.org/abs/astro-ph/0702244v1

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Sep 22, 2013
09/13

by
Lu Yang; Shekhar Garde

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Partitioning and transport of water and small solutes into and through nanopores is important to a variety of chemical and biological processes and applications. Here we study the partitioning of positive ions of increasing size into the pore interior using extensive molecular dynamics simulations. Despite the simplicity of the simulation system, the results provide new and useful insights on both the pore hydration and ion partitioning. For low negative charge densities on the pore, the...

Source: http://arxiv.org/abs/physics/0702065v1

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Jul 20, 2013
07/13

by
Götz S. Uhrig

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A general strategy to maintain the coherence of a quantum bit is proposed. The analytical result is derived rigorously including all memory and back-action effects. It is based on an optimized $\pi$-pulse sequence for dynamic decoupling extending the Carr-Purcell-Meiboom-Gill (CPMG) cycle. The optimized sequence is very efficient, in particular for strong couplings to the environment.

Source: http://arxiv.org/abs/quant-ph/0609203v2

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Sep 18, 2013
09/13

by
J-M. L. Beaujour; W. Chen; K. Krycka; C-C. Kao; J. Z. Sun; A. D. Kent

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We report on room temperature ferromagnetic resonance (FMR) studies of [$t$ Co$|2t$ Ni]$\times$N sputtered films, where $0.1 \leq t \leq 0.6$ nm. Two series of films were investigated: films with same number of Co$|$Ni bilayer repeats (N=12), and samples in which the overall magnetic layer thickness is kept constant at 3.6 nm (N=1.2/$t$). The FMR measurements were conducted with a high frequency broadband coplanar waveguide up to 50 GHz using a flip-chip method. The resonance field and the full...

Source: http://arxiv.org/abs/cond-mat/0611027v2

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Sep 18, 2013
09/13

by
J. D. Fletcher; A. Carrington; P. Diener; P. Rodiere; J. P. Brison; R. Prozorov; T. Olheiser; R. W. Giannetta

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We report measurements of the temperature dependence of both in-plane and out-of-plane penetration depths ($\lambda_a$ and $\lambda_c$ respectively) in 2\textit{H}-NbSe$_2$. Measurements were made with a radio-frequency tunnel diode oscillator circuit at temperatures down to 100 mK. Analysis of the anisotropic superfluid density shows that a reduced energy gap is located on one or more of the quasi-two-dimensional Nb Fermi surface sheets rather than on the Se sheet, in contrast to some previous...

Source: http://arxiv.org/abs/cond-mat/0605059v2

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27

Sep 22, 2013
09/13

by
Yun-Song Piao

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Recently, it has been shown in Ref.[1] that the string thermodynamic fluctuation may lead to a scale invariant spectrum of scalar metric perturbation. However, its realization is still in study. In this note we suppose that the correlation length of metric perturbation, which is proportional to the sound speed, might be nearly divergent at the critical point of phase transition. In this case we find that the string gas mechanism responsible for the generation of primordial perturbation may be...

Source: http://arxiv.org/abs/gr-qc/0702012v2

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25

Sep 22, 2013
09/13

by
François Caron; Manuel Davy; Arnaud Doucet; Emmanuel Duflos; Philippe Vanheeghe

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Using Kalman techniques, it is possible to perform optimal estimation in linear Gaussian state-space models. We address here the case where the noise probability density functions are of unknown functional form. A flexible Bayesian nonparametric noise model based on Dirichlet process mixtures is introduced. Efficient Markov chain Monte Carlo and Sequential Monte Carlo methods are then developed to perform optimal batch and sequential estimation in such contexts. The algorithms are applied to...

Source: http://arxiv.org/abs/math/0702225v1

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26

Sep 22, 2013
09/13

by
Y. Tsue; H. Fujii; Y. Hashimoto

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We investigate the chiral phase transition of a QCD-like theory, based the shape change of the effective potential near the critical point. The potential is constructed with the auxiliary field method, and a source term coupled to the field is introduced in order to compute the potential shape numerically. We also generalize the potential so as to have two independent order parameters, the quark scalar density and the number density. We find a tri-critical point locating at (T,mu)=(97, 203)...

Source: http://arxiv.org/abs/hep-ph/0702082v1

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20

Sep 22, 2013
09/13

by
Denis Gouvêa Ladeira; Jafferson Kamphorst Leal da Silva

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The chaotic sea below the lowest energy spanning curve of the complete Fermi-Ulam model (FUM) is numerically investigated when the amplitude of oscillation 'epsilon' of the moving wall is small. We use scaling analysis near the integrable to non-integrable transition to describe the average energy as function of time t and as function of iteration (or collision) number n. If t is employed as independent variable, the exponents related to the energy scaling properties of the FUM are different...

Source: http://arxiv.org/abs/nlin/0702018v1

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Sep 22, 2013
09/13

by
Wen-Cong Chen; Xiang-Dong Li

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Recent investigations on the delay time of type Ia supernovae have set useful constraints on the progenitors of type Ia supernovae. Here we have calculated the evolution of close binaries consisting of a white dwarf and a main-sequence or subgiant companion. We assume that, once Roche lobe overflow occurs a small fraction of the lost mass from the system forms a circumbinary disk, which extracts the orbital angular momentum from the system through tidal torques. Our calculations indicate that...

Source: http://arxiv.org/abs/astro-ph/0702218v1